This application relates to a system and process for precise measurement and adjustment of waveplate retardation using a photoelastic modulator.
A waveplate is an optical device that resolves a linear polarized light wave into two orthogonal, linear polarized components and produces a phase shift between them. Thus, the polarization state of the light beam is altered. Waveplates, which are often referred to as retarders, are useful in applications requiring control or analysis of the polarization states of light.
In some applications it is necessary to measure or calibrate the retardation of a waveplate that is used in an experimental or analytical optical setup. Such calibration will account for any variations from the specified retardation of a particular waveplate.
Moreover, in some instances it may be desirable to vary slightly the retardation provided by a waveplate that is used in an optical setup, without replacing or physically modifying the waveplate.
The present invention is directed to a practical system and method for measuring waveplate retardation. The system employs a photoelastic modulator in an optical setup and provides high sensitivity. The analysis is particularly appropriate for quality-control testing of waveplates.
The system of the present invention is also adaptable for slightly varying the retardation provided by a waveplate (or any other retarder device) in a given optical setup. Such xe2x80x9cfine tuningxe2x80x9d of the retardation provided by the waveplate is useful in high-precision analyses. To this end, the waveplate position may be precisely altered to introduce correspondingly precise adjustments of the retardation values that the waveplate provides.
The present invention is further refined to permit one to compensate for errors in the retardation measurements just mentioned. Such errors may be attributable to static birefringence present in the optical element of the photoelastic modulator that is incorporated in the system.